The mechanisms of intestine water and electrolyte secretion will be investigated in normal intestine and in intestinal secretory states induced by purified cholera toxin, cyclic AMP, theophylline, and hormones such as gastrin and thyrocalcitonin. The experimental techniques used will be primarily in vitro studies with the Ussing Chamber technique, combined with measurements of cyclic nucleotides (cAMP and cGMP) within the intestinal mucosa. The mechanism of acetylsalicylic acid inhibition of chloera toxin stimulated intestinal secretion will be explored. Such investigations at the cellular level should define the basic ionic transport mechanisms responsible for intestinal secretion, and should give insight into the pathophysiology of various diarrheal states. In addition, water and electrolyte transport by the rabbit esophagus will be studied with an in vivo perfusion technique and by the esophageal stratified squamous epithelium stripped of its muscular layer with the in vitro Ussing chamber technique. These studies should demonstrate that the mammalian esophagus is an organ capable of water and electrolyte transport, should define the ionic pumps responsible for this capability, and define the nature of the transmural electrical potential difference in this organ.